An apparatus for deep drawing a thermoplastic foil for the manufacture of blister packs as used in the packaging of pills or the like has an upper tool and a lower tool that are movable relative to each other and to a foil plane extending between them. As described in EP 1,297,943 the lower tool can be moved by a first actuator, and the upper tool is provided with an extender on a rod that is mounted on another actuator. The upper tool also has a separate seal piston that has its own actuator. With this apparatus the foil extending between the upper tool and the lower tool is first gripped by moving the lower tool and then is stretched by advance of the extender, and finally is given its final shape by movement of the seal piston. The numerous independent drives complicate this apparatus and make it expensive and cost inefficient.
The thermoshaper in WO 01/43947 of Hilpert has a complex arrangement of a spring-loaded hold-down plate and means for feeding air pressure through individual plungers to the foil to assist in the thermal deformation. This arrangement is complicated and requires substantial refitting when the arrangement of the blisters to be formed changes.
Similarly, German 41 35 935 uses a lower tool having an array of cavities that can be evacuated to form blisters in the foil. Such an arrangement also requires a complex and expensive lower tool and makes it very difficult to change blister format.